The increased sensitivity of asthmatics to inhaled isoprenaline suggests that they may also be more sensitive to their endogenous adrenaline, which may thus dilate and stabilize their airways. Taken with enhanced antagonism by propranolol, this provides insight into the aggravation of asthma by beta-blocking drugs.

The prevalence of smoking was studied using a questionnaire. Pulmonary function tests and respiratory symptoms were evaluated in 176 smokers. The total studied population with family and co-workers were 13289. The number of smokers among studied population was 11.7%. The rate of smoking among male subjects was 17.2% and in female 2.5%. All values of PFTs in smokers were significantly lower (p<0.001) and respiratory symptoms higher than in non smokers (p<0.05 for cough and p<0.001 for wheeze and tightness). There were significant negative correlations between smoking duration and rate with values of PFT (p<0.05-p<0.001). In this study the prevalence of smoking in population of Mashhad city was shown. The prevalence of smoking was higher among male than females. Smoking leads to increased respiratory symptoms and reduction of PFTs values.

Despite the controversy of bronchial responsiveness to β₂-agonist drugs in asthma, in a previous study we have shown increased responsiveness of asthmatic tracheobronchial tree to isoprenaline. Therefore, in the present study, tracheal responsiveness to isoprenaline and also β-adrenergic receptor blockade were studied in sensitized guinea pigs. An experimental model of asthma was induced in guinea pigs by sensitization of animals with injection and inhalation of ovalbumin (OA). The responses of tracheal chains of sensitized and control animals to cumulative concentrations of isoprenaline (I) in the absence and presence of 10 nmol/l propranolol were measured, and the effective concentration of I causing 50% of maximum response (EC₅₀ I) was obtained. The propranolol blockade (CR – 1) was calculated by: (post-propranolol EC₅₀ I/EC₅₀ I) – 1. Tracheal responses of sensitized and control animals to cumulative concentrations of methacholine (M) were also measured and EC₅₀ M were obtained. The tracheal responses of sensitized guinea pig to isoprenaline was significantly higher than that of the control animals (EC₅₀ I for sensitized and control animals were 0.24 ± 0.04 and 0.58 ± 0.07 µmol/l, respectively; p < 0.001).The β-adrenergic receptor blockade by propranolol (CR – 1) was also significantly higher in sensitized guinea pigs than that of the control animals (p < 0.001). The results of this study indicate an increased tracheal response to β-adrenergic-stimulating drug and enhancement of β-adrenergic blockade by propranolol in the sensitized guinea pig.